Method for intermittently depositing particulate material in a substrate

ABSTRACT

A method for forming a zoned distribution of particulate material within a fibrous web includes a conveying step for providing a gas entrained supply of the particulate material and a segregating step centrifugally directing at least a portion of the particulate material into an accumulation region. A transferring step selectively directs particulate material from the accumulation region into a delivery gas stream to provide an intermittent flow volume of a selected quantity of particulate material from the accumulation region through a delivery conduit and into a web forming chamber. A fiberizing step provides a flow of a selected fibrous material into the web forming chamber, and a directing step controls the intermittent flow of particulate material from the delivery conduit into the forming chamber. A foraminous forming layer is disposed within the forming chamber for receiving the fibrous material and the particulate material to produce a fibrous web which includes zoned regions having selected, different amounts of the particulate material therein.

This is a divisional application of copending application Ser. No.07/462,363, filed on Jan. 9, 1990, now U.S. Pat. No. 2,028,224.

THE FIELD OF THE INVENTION

The present invention relates to a method and apparatus for forming azoned distribution of particulate material within a fibrous web. Moreparticularly, the present invention relates to a method and apparatusfor forming a zoned distribution of superabsorbent polymer particleswithin an absorbent pad composed of hydrophilic fibers.

BACKGROUND OF THE INVENTION

Absorbent articles, such as disposable infant diapers, feminine careproducts, incontinence garments and the like, have included highabsorbency superabsorbent polymers to increase the absorbent capacity ofthe article and to reduce the bulkiness of the article. For example, seeU.S. Pat. No. 3,669,103 to Harper, U.S. Pat. No. 3,670,731 to Harmon,and U.S. Pat. No. 4,087,506 to Cook et al. Particular absorbent articledesigns have concentrated superabsorbent polymers in selected regions ofthe absorbent pad. For example, see U.S. Pat. No. 4,381,782 to Mazuraket al., U.S. Pat. No. 4,410,324 to Sabee and U.S. Pat. No. 4,461,621 toKarami et al.. In some of these conventional arrangements, the highabsorbency material, such as superabsorbent polymer, have beensubstantially uniformly mixed with absorbent fibers located withinselected layers, or strips. In other arrangements, the high absorbencymaterial has been substantially isolated in layers, zones or pocketswithin the absorbent pad with the high absorbency material substantiallyunmixed with the absorbent fibers.

Various devices and processes have been employed to manufactureabsorbent article designs. Air forming techniques for forming webs ofhydrophilic fibers, such as woodpulp fibers, are well known in the art.In addition, it is well known that superabsorbent polymers may be mixedwith the hydrophilic fibers during an airlaying process to form anabsorbent web. For example, see the Sanyo Technical Bulletin entitled"SAP SHEET", dated October 1982.

Particular absorbent article designs have particles of superabsorbentpolymer localized in selected regions. For example, U.S. Pat. No.3,888,257 issued June 10, 1975 to R. Cook et al. describes a disposableabsorbent article in which a rectilinear, central zone of a matrix offiberized woodpulp incorporates a 3-dimensional dispersion ofhydro-colloid polymer particles. U.S. Pat. No. 4,381,782 issued May 3,1983 to P. Mazurak et al. describes an absorbent article whereinhydrogel material is incorporated by placement near a front edge of anabsorbent batt in a diaper article. Other designs have incorporatedsuperabsorbent materials within selected layers, longitudinal strips,lateral strips and other types of isolated zones or regions.

Various methods and apparatus have been employed to manufactureabsorbent articles. For example, U.K. Patent Application, GB 2,150,033 Apublished June 26, 1985, describes a suction drum apparatus for makingan absorbent pad wherein an integrated shell of flocculent materialsurrounds an internal absorbent layer. U.S. Pat. No. 4,087,508 issuedMay 2, 1978 to R. Cook et al. describes a method which includes applyinghydrocolloid polymer particles onto the surface of a central zone of amoving web, and distributing the applied particles into the body of themoving web by air-pressure means. International Patent Application No.WO 88/04165 published June 16, 1988 described a method and apparatus forforming a nonwoven pad consisting of fibrous material in which highlymoisture-absorbent particles are intermixed with the fibrous materialthroughout a predetermined portion of the thickness of the nonwoven pad.A spray gun or an extension thereof is positioned within the chamberrelative to the fibrous material atop a conveyor and is operated todischarge moisture-absorbent material at a predetermined velocity, suchthat the moisture-absorbent material is intermixed with the fibrousmaterial throughout a central layer of the thickness of the nonwoven padwhile forming boundary layers on either side of the center layer whichare substantially free of moisture-absorbent material. The spray gunpreferably operates intermittently to form spaced, sharply defined areasalong the length and width of the nonwoven pad wherein each area hasmoisture absorbent material interspersed throughout a portion of thethickness thereof.

Conventional methods and apparatus, such as those described above, havenot been sufficiently satisfactory. For example, the devices may beoverly complex and expensive and may not provide desired patterns ofdeposition for particulate materials, such as superabsorbent granules.The rate of delivery of the superabsorbent particles may not beadequately controlled, and the systems may be excessively sensitive tochanging bulk densities in the particulate material.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a distinctive technique for forming azoned distribution of particulate material within a fibrous web.Generally stated, an apparatus of the invention comprises conveyingmeans for providing a gas entrained supply stream of the particulatematerial, and segregating means for centrifugally directing at least aportion of the particulate material into an accumulation region of theapparatus. Transferring means selectively direct particulate materialfrom the accumulation region into a delivery gas stream to provide anintermittent flow of a selected quantity of particulate material fromthe accumulation region through a delivery conduit and into a webforming chamber. Fiberizing means provide a flow of a selected fibrousmaterial into the web forming chamber, and directing means control theintermittent flow of particulate material from the delivery conduit intothe forming chamber. A foraminous forming layer is disposed within theforming chamber for receiving the fibrous material and the particulatematerial to form a fibrous web which includes zoned regions havingselected, different amounts of the particulate material therein.

The present invention can further provide a method for forming a zoneddistribution of particulate material within a fibrous web. In thisaspect of the invention, the method comprises the steps of providing agas entrained supply stream of the particulate material, andcentrifugally directing at least a portion of the particulate materialinto an accumulation region. The particulate material is selectivelytransferred from the accumulation region into a delivery as stream toprovide an intermittent flow of a selected quantity of particulatematerial from the accumulation region through a delivery conduit andinto a web forming chamber. A flow of a selected fibrous material isprovided into the web forming chamber, and the intermittent flow ofparticulate material from the delivery conduit into the forming chamberis selectively controlled. The fibrous material and particulate materialare received on a foraminous forming layer located within the formingchamber to produce a fibrous web which includes zoned regions havingselected, different amounts of the particulate material therein.

Yet another aspect of the invention is a distinctive absorbent articlecomprising a substantially unitary web composed of a mass of hydrophilicfibers, and a quantity of superabsorbent polymer particles locatedwithin the fibrous mass. The superabsorbent particles have adistinctive, nonuniform distribution along a longitudinal, lengthdimension of the web. The weight percentage of superabsorbent (per unitweight of the combined particles and fiber) is also nonuniformlydistributed along the length dimension. In particular aspects of theinvention, the article can include a longitudinal, length-wise particledistribution which is substantially configured in the form of two ormore stepped stages.

The present invention can advantageously provide a method and apparatuswhich, when compared to conventional devices, can more efficientlylocalize particulate material within selected regions of a fibrous web,and can position the particulate material in a manner which is generallyindependent of the flow of fibrous material employed to form the web. Asa result, the present invention can advantageously provide an airlaid,intermingled structure wherein larger proportions of particles can beplaced at selected locations without concomitantly placing largerproportions of fibrous material at those locations. The apparatus canalso have lower complexity and lower costs while affording sufficientcontrollability to provide desired patterns of particulate distributionwithin the fibrous web. In particular aspects of the invention, themethod and apparatus can provide lower weight variability betweenindividual quantities of delivered particulate material and canadvantageously be arranged to automatically detect problems within thesystem. In other aspects of the invention, the method and apparatus canbe less sensitive to the flow characteristics of the particulatematerial and can advantageously be configured to have fewer transientflow conditions caused by repetitively accelerating and/or deceleratingthe flow of particulate material. Difficulties in adequately controllingtransient flow conditions may cause undesired variations in the amountof material contained in the individual particulate quantities. Afurther advantage of the invention is that the method and apparatus canoperate at high speeds. For example, the method and apparatus may beconfigured to deliver 600 or more substantially discrete quantities ofparticulate material per minute.

The distinctive absorbent article of the invention can advantageouslyprovide a more efficient use of the absorbent material and provide amore effective, localized placement of superabsorbent particles within aweb or pad composed of hydrophilic fibers. In addition, the absorbentarticle of the invention may advantageously incorporate a selectivelyzoned placement of two or more different types of particulate material.For example, the article may include two or more different types ofsuperabsorbent material, each of which has a distinctive set ofabsorption characteristics and is differently located within a fibrousweb.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood and furtheradvantages will become apparent when reference is made to the followingdetailed description of the invention and the drawings, in which:

FIG. 1 representatively shows a schematic, system diagram of theinvention;

FIG. 2 representatively shows an embodiment of the invention whichincludes a pulsing mechanism for producing an intermittent flow ofparticles;

FIG. 3 shows a schematic representation of a phasing control systememployed in the present invention;

FIGS. 4 and 4A representatively show an embodiment of the inventionwhich includes a diverter mechanism for producing intermittent flow;

FIG. 5 representatively shows a forming chamber employed with thepresent invention;

FIG. 6 representatively shows an embodiment of the invention whichincludes a combination of mechanisms for producing different flows ofparticulate material;

FIGS. 7, 7A and 7B respectively show representative side, top and endviews of a "doughnut" configuration of the segregating mechanism of theinvention;

FIGS. 8 and 8A representatively show a metered, flow splittingmechanism;

FIG. 9 representatively shows a particle recovery system employed withthe present invention;

FIG. 10 representatively shows an absorbent diaper-type article whichincorporates an absorbent body of the present invention;

FIGS. 11 and 11A show a schematic block diagram of a pulser-type system,and a graphic representation of the distribution of particulate materialproduced along a longitudinal dimension of a fibrous web by such asystem, respectively;

FIGS. 12 and 12A show a schematic block diagram of a diverter-typesystem, and a graphic representation of the distribution of particulatematerial produced along the longitudinal dimension of the fibrous web bysuch a system, respectively;

FIGS. 13 and 13A show a schematic block diagram of an apparatuscomprising two pulser-type systems, and a graphic representation of thedistribution of particulate material produced along the longitudinaldimension of the fibrous web by such an apparatus, respectively;

FIGS. 14 and 14A show a schematic block diagram of an apparatuscomprising a pulser-type system and a diverter-type system, and agraphic representation of the distribution of particulate materialproduced along the longitudinal dimension of the fibrous web by such anapparatus, respectively;

FIGS. 15, 15A and 15B respectively show a schematic block diagram of adiverter-type system capable of providing a plurality of discrete openpositions, examples of three discrete diverter positions, and a graphicrepresentation of the distribution of particulate material producedalong the longitudinal dimension of the fibrous web by such a system;

FIG. 16 shows a graphic representation of several bilobal distributionsof particulate material produced along the longitudinal dimension of thefibrous web;

FIGS. 17 and 17A show graphic representations of regions along thelength of an article of the invention wherein article regions withhigher amounts of superabsorbent are in-phase with the article regionswith higher amounts of fibrous material;

FIG. 18 shows a graphic representation of sequential regions along thelength of a conventional diaper wherein the superabsorbent particles aresubstantially uniformly distributed along the diaper length;

FIGS. 19 and 19A show graphic representations of regions along thelength of an article of the invention wherein article regions withhigher amounts of superabsorbent are in-phase with article regions withhigher amounts of fibrous material;

FIG. 19B shows a graphic representation of regions along the length ofan article of the invention wherein article regions with higher amountsof superabsorbent are out-of-phase with article regions with higheramounts of fibrous material;

FIGS. 20 and 20A show graphic representations of regions along thelength of another article of the invention wherein article regions withhigher amounts of superabsorbent are out-of-phase and offset fromarticle regions with higher amounts of fibrous material; and

FIG. 21 show a graphic representation of regions along the length of anarticle of the invention wherein article regions with higher amounts ofsuperabsorbent are further out-of-phase and offset from article regionswith higher amounts of fibrous material.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description will be made in the context ofdepositing superabsorbent particles within a web employed to constructan absorbent body for use in a disposable diaper article. It should beunderstood, however, that the present invention may also be employed toincorporate other types of particulate material within a mass ofhydrophilic or hydrophobic fibers. In addition, it should be readilyunderstood that the present invention may also be employed to produceabsorbent bodies for other types of absorbent articles, such as femininecare products, incontinence garments and the like. All of suchalternative configurations are contemplated as being within the scope ofthe present invention.

The invention is particularly useful for depositing particles of organicor inorganic high-absorbency (e.g. superabsorbent) material within afibrous web. Suitable inorganic high-absorbency materials include, forexample, absorbent clays and silica gels. Organic high-absorbencymaterials can include natural materials, such as agar, pectin, guar gumand peat moss, as well as synthetic materials, such as synthetichydrogel polymers. Such hydrogel polymers include, for example,carboxymethylcellulose, alkali metal salts of polyacrylic acids,polyacrylamides, polyvinyl ethers, hydroxypropyl cellulose, polyvinylmorpholinone, polymers and copolymers of vinyl sulfonic acid,polyacrylates, polyacrylamides, polyvinyl pyridine and the like. Othersuitable polymers include hydrolyzed acrylonitrile grafted starch,acrylic acid grafted starch, and isobutylene maleic anhydridecopolymers, and mixtures thereof. The hydrogel polymers are preferablylightly cross-linked to impart desired levels of water insolubility tothe material. Crosslinking may, for example, be by irradiation or bycovalent, ionic, Van der Waals, or hydrogen bonding. Suitable materialsare available from various commercial vendors, such as Dow ChemicalCompany, Hoechst Celanese Corporation, Allied-Colloid, and Stockhausen.Typically, the high-absorbency material is capable of absorbing at leastabout 15 times its weight in water, and preferably

is capable of absorbing at least about 25-50 times its weight in water.

The particles of high absorbency material may have regular shapes orirregular shapes, such as elongated forms. For example, particles ofhigh-absorbency material may be configured in the form of granules,flakes, fibers, or the like. The particles typically measure about50-1000 micrometers in size, preferably measure about 100-800micrometers, and more preferably measure about 200-600 micrometers insize to provide improved processability through the apparatus of theinvention.

With reference to FIG. 1, a representative apparatus of the invention isconfigured to form a zoned distribution of particulate material, such asparticles 10 of a superabsorbent polymer material (SAM), within afibrous web 42, such as a web comprising woodpulp fluff fibers. Aconveying means, such as a mechanism composed of particle feeder 14 andconveying blower 16, provides a gas entrained supply stream ofsuperabsorbent polymer particles. A segregating means 20 centrifugallydirects at least a portion of the particulate material into anaccumulation region of the apparatus. Transferring means 24 selectivelydirects the particulate material from the accumulation region into adelivery gas stream 26 supplied by delivery blower 28 to provide atime-varying, intermittent flow of selected, controlled quantities ofparticulate material from the accumulation region through a deliveryconduit 30 into a web forming chamber 32. Fiberizing means, such ashammermill 34 provides a flow of a selected fibrous material, such aswoodpulp fluff fibers, into the web forming chamber. A directing means,such as delivery nozzle 36, controls the intermittent flow ofsuperabsorbent particles from delivery conduit 30 into forming chamber32, and a foraminous forming layer 38 is moveable and disposed withinthe forming chamber to receive fluff fibers 40 and particles 10 thereonto form fibrous web 42. The fibrous web includes distinctive, zonedregions having selected, different amounts of particulate materialtherein. The supply stream of gas/particles can be recirculated tofeeder device through a suitable conduit, and a particle recovery system39 may be employed to separate the particles from the gas for returninto a supply reservoir of the feeder device. The residual gas exitsfrom the recovery system through gas exhaust section 136.

The method and apparatus of the invention can advantageously operate athigh speeds. For example, the method and apparatus may be configured todeliver 600 or more substantially discrete quantities of particulatematerial per minute, and in particular embodiments, the invention can beconfigured to deliver at least 1000 substantially discrete quantities ofparticulate material per minute.

The illustrated embodiment of the invention is shown as having aconveying blower 16 and delivery blower 28 which are physically separatefrom each other. It should be readily appreciated, however, that theseparate functions provided by the conveying blower and delivery blowermay be provided by a single, combined mechanism, such as a singleblower. For example, the residual gas exiting from exhaust section 136of recovery system 39 may be recirculated with suitable connectingconduits (dashed line of arrows) to provide delivery gas stream 26.Accordingly, the delivery gas stream may be composed of the residual gasstream from recovery system 39. With this arrangement, blower 28 may beeliminated, and blower 16 may advantageously be employed to generateboth conveying gas stream 46 and delivery gas stream 26 in a moreefficient system.

Feeder device 14 includes a particulate regulating means for providing aselected mass flow rate of high absorbency particles, such as particlescomposed of superabsorbent hydrogel polymer, into a conveying gas stream46 provided by conveying blower 16. It should be readily understood thatthe amount of superabsorbent polymer delivered into conveying gas stream46 is dependent upon the forming rate of web 42 and the weight percentof particles desired to be contained within the web. In the illustratedembodiment, the particulate regulating means is constructed andconfigured to provide a particulate mass flow rate which is within therange of about 6-90 gm/sec. Various types of feeder mechanisms may beemployed with the present invention. Preferably, the invention employs a"weight-in loss" type of feeder system which can take into account theamount of polymer being returned into reservoir 15 from particlerecovery system 39 and automatically adjust the amount of polymer beingfed into supply stream 18. This device can thereby help control thedelivery of the desired amounts of polymer into web 42. In the shownembodiment, the feeder device may be a LWF3-35 feeder manufactured byK-tron Corp., a company located in Pitman, N.J. Other equivalent devicesmay also be employed with the present invention.

Various types of commercially available blower devices may be employedwith the present invention. In the shown embodiment, conveying blower 16may be a VB-019 blower manufactured by Spencer ab 30 Turbine, a companylocated in Windsor, Conn.

In particular embodiments of the invention, conveying blower 16 isconfigured to supply a conveying gas flow velocity of not less thanabout 5 m/sec (about 1000 ft/min), and preferably provides a gasvelocity of not less than about 9 m/sec (about 1800 ft/min). In otherembodiments of the invention, conveying blower 16 is configured toprovide a gas velocity in conveying gas stream 46 of not more than about35 m/sec (about 7000 ft/min), and preferably provides a velocity of notmore than about 45 m/sec (about 8500 ft/min) to provide improvedperformance. A suitable conveying conduit 17 is employed to transportthe particle/gas mixture composed of the superabsorbent particlesentrained in the moving stream of conveying gas.

Proper conveying gas flow is dependent on the material being conveyed.In addition to the velocity ranges given, it is desirable to maintainthe "solids loading ratio" (mass flow rate of material divided by themass flow rate of conveying gas) below about 5. Preferably, the solidsloading ratio is maintained below about 3. At these ratios, theresultant two-phase flow is typically classified as "lean phase". Leanphase flow is desirable to minimize short-term weight variability.

Referring now to FIG. 2, particulate/gas supply stream 18 moves into asegregating means 20 for centrifugally directing at least a portion ofthe superabsorbent particles 10 into an accumulation region 22 of theapparatus. In the illustrated embodiment, the segregating means includesan arcuate, curved conduit 48 having a radiused bend through whichsupply stream 18 moves to operably concentrate the superabsorbentparticles in an accumulation region comprising a zone located toward aradially outward wall 50 of the curved conduit. Within supply stream 18,the superabsorbent particles may be randomly or substantially uniformlydistributed within the entraining stream of moving transport gas. As theparticle/gas mixture moves through the curved path provided by conduit48, the momentum and dynamic inertia ("centrifugal force") of the movingparticles causes the particles to displace the less dense conveying airand hug outward wall 50. The particles concentrate along wall 50 as thewall provides the centripetal force needed to accelerate and bend themovement of the particles along the curved path defined by conduit 48.As a result, particles 10 are operably segregated toward the radiallyoutward wall 50 of the curved conduit.

In a particular aspect of the invention, curved conduit 48 traverses acurved, generally circular arc subtended by an angle of not less thanabout 30 degrees, and preferably traverses an arc subtended by an angleof not less than about 60 degrees. In a further aspect of the invention,curved conduit 48 traverses a curved, substantially circular arcsubtended by an angle of not more than about 360 degrees, and preferablytraverses an arc subtended by an angle of not more than about 300degrees to provide desired advantages.

Curved conduit 48 has an inlet section 52 and an outlet section 54.Supply stream 18 enters through inlet 52 and the residual supply streamdeparts the curved conduit from outlet section 54. Depending upon theparticular operating condition of the segregating means, the residualsupply stream may contain lesser amounts of superabsorbent particlesthan the original supply stream entering inlet section 52.

Where curved conduit 48 traverses an arc of greater than 180 degrees, itwill be appreciated that there may be a crossing of the paths defined byinlet section 52 and outlet section 54. Accordingly, the inlet andoutlet sections of conduit 48 may need to be physically offset from eachother to avoid interference. Such a configuration may cause curvedconduit 48 to define a generally "cork-screw", approximately helicalpath. For the purposes of the present invention, such a path shape iscontemplated as being included within the meaning of the term, circular.

Another embodiment of the invention, representatively shown in FIG. 7,7A and 7B, comprises a curved conduit 48 configured in a generally"doughnut" shape. In the illustrated embodiment, the curved conduit iscircular and includes a dividing wall member 53, which operablyseparates inlet section 52 from outlet section 54. The openingscommunicating into inlet section 52 and out from outlet section 54 maybe arranged in any operable configuration. For example, supply stream 18may enter inlet section 52 and exit outlet section 54 through the sidesof the doughnut-shape, along directions which are generallyperpendicular to the plane defined by the doughnut-shape. Alternatively,supply stream 18 may enter the inlet section (as illustrated) or exitthe outlet section (not as illustrated) along a direction generallyaligned with a radius of the doughnut-shape.

Curved conduit 48, in particular aspects of the invention, has a radiusof curvature 56 of not less than about 5.08 cm (about 2 in), andpreferably has a radius of curvature of not less than about 13 cm (about5 in). In addition, the curved conduit has a radius of curvature of notmore than about 5 m (about 197 in), and preferably has a radius ofcurvature of not more than about 1 m (about 39 in) to provide improvedeffectiveness. The shown embodiment of the invention has a radius ofcurvature about 15 cm (about 6 in) as determined by measuring from thefocus or center of curvature out to the radially outward wall 50 of thecurved conduit.

Referring again to FIG. 2, the shown embodiment of the inventionincludes a transferring means comprising a separating means, such asblade member 72, for selectively guiding a predetermined, meteredquantity 64 of the particulate material from accumulation region 22 intoreceiving chamber 62. The receiving chamber gathers and temporarilyholds the particles, and a suitable gas supplying means 58 provides atleast a portion of a delivery gas stream 26 to move the selectedquantity of particulate material 64 from receiving chamber 62 intodelivery conduit 30. A controlling means, such as an electromechanicalrelay or an electronic, solid-state relay 66, selectively operates andregulates gas supplying means 58 to provide an initial delivery gasstream 26a which entrains and intermittently propels particulatequantity 64 into delivery conduit 30 in a sequentially pulsed manner.

The embodiment of the invention illustrated in FIG. 2 can advantageouslyprovide a distinctive, improved pulsing system for supplying theregulated, metered quantities of superabsorbent particles. The shownembodiment of the pulsing system can be conceptualized as working in twostages. First it employs a segregating means to separate and collect,then it employs a transferring means to release and deliver.

In the illustrated embodiment of the separating and collectingoperations, a substantially continuous conveying stream composed of amixture of superabsorbent particles and gas (air) enters inlet section52 of curved conduit 48. The particles/air mixture flows around thecurved conduit, and the relatively greater momentum and inertia("centrifugal force") of the particles causes the more dense particulatematerial to gather along and hug the radially outward wall 50 of theconduit pipe. This operation creates a stratified mixture within conduit48 within which the flowing particles are concentrated in accumulationregion 22 of the conduit. When the stratified mixture reaches separatingblade 72, nearly all of the particulate material is flowing along outerwall 50. As a result, a major portion 78 of the conveying air flows overthe top of the separating blade. Concurrently, the moving stream ofsuperabsorbent particles and a minor portion 79 of the conveying air aredirected into receiving chamber 62. A wire mesh screen 74 is located atone end of receiving chamber 62 and the movement of the particle streamis directed against the screen to stop and collect the superabsorbentparticles. The size of the screen mesh is sufficiently small tosubstantially prevent the passage of superabsorbent particlestherethrough. As a result, the particles are operably collected withinchamber 62, and further segregated from the conveying air stream as theminor portion of conveying air 79 operably deflects away from thecollected particles and departs from chamber 62 through exit opening 76.

To release and deliver the particles, flow regulating means such ascontrol valve 68 can be triggered at a selected time to deliver aregulated, timed burst of initial delivery air 26a, which is directedthrough screen 74 from a suitable gas supplying means 58. The air blastpushes the collected superabsorbent particles through receiving chamber62 and out an open, exit end 76 of the receiving chamber.

In an alternative configuration of the invention, the release anddelivery of the particles may optionally be accomplished with apiston-type mechanism. The piston can be selectively actuated with aconventional drive mechanism, such as a pneumatic actuator, a mechanicalcam mechanism or a driven linkage actuated by an electromechanicalservo, to operably push or otherwise force the collected quantity ofsuperabsorbent particles back into the minor portion 79 of the conveyingairstream. Conveying air portion 79 can then entrain the particles andcarry them out the exit end of the receiving chamber into delivery airstream 26.

Meanwhile, the major portion 78 of conveying air stream 46, whichportion was initially separated from the superabsorbent particles,continuously flows through recirculation conduit 80 and is directed toflow through a generally annular region which is circumferentiallyadjacent to at least a portion of the outside of receiving chamber 62.As a result, this air stream is effectively converted and reconfiguredto become a delivery gas stream portion 26b, which flows past chamber 62and then away from the chamber through outlet conduit 82. As gas streamportion 26b flows past chamber 62, the gas stream combines with theresidual conveying air portion 79 departing the chamber. Each pulse ofsuperabsorbent particles departing from receiving chamber 62 is conveyedthrough outlet 82 into delivery conduit 30, and during this operation,the air/particle pulse merges into and flows along with gas streamportion 26b.

The resultant, combined delivery air stream 26 moving through conduit 30includes a series of intermittent, spaced-apart pulse regions each ofwhich comprises a mixture of air and superabsorbent particles.Interposed between the spaced-apart, pulse regions are air stream bufferregions which contain lesser amounts of particles and, preferably, aresubstantially free of superabsorbent particles. As the pulse regionsmove through delivery nozzle 36 (FIG. 1), the particle/air pulses can beselectively shaped and released into forming chamber 32. The particleswithin the pulse have a relatively high velocity, for example, about3000 feet/minute (about 15 meters/sec), and the momentum of theparticles carries the particles from nozzle 36 to traverse particular,predictable distances through forming chamber 32 to deposit into theselected substrate, such as a fibrous web.

Various types of conventional control valves and control relays may beemployed with the present invention. In the illustrated embodiment,solenoid control valve 68 may be a 56C-61-1-CA valve manufactured by MACValves, Inc. located in Wixom, Mich. The control relay 66 may be asolid-state relay, such as an ODC5 relay manufactured by OPTO 22, abusiness located in Huntington Beach, Calif.

Gas supplying means 58 delivers air at a pressure of not more than about30 psi (about 207 kPa), and preferably delivers air at a pressure of notmore than about 20 psi (about 138 kPa). The corresponding peak velocityof the delivered air is about 9000 ft/min (about 46 m/sec). In addition,gas supplying means 58 can be configured to deliver air at a pressure ofnot less than about 1 psi (about 7 kPa), and preferably at a pressure ofnot less than about 3 psi (about 21 kPa) to provide improvedeffectiveness. The corresponding peak velocity of the delivered air isabout 1000 ft/min (about 5 m/sec). In the shown embodiment, gassupplying means 58 delivers clean, dry, compressed air at a pressure ofabout 6 psi (about 41 kPa) with a peak air velocity of about 3000 ft/min(about 15 m/sec).

To properly control and sequence the desired placement of particulatequantities 64 within fibrous web 42 (FIG. 1), an aspect of the inventionincludes a phasing means for sequencing the operation of transferringmeans 24 to provide a desired registration between particulate quantity64 and a selected deposition region along a machine direction of fibrousweb 42. A particular embodiment of the invention includes the phasingcontrol system representatively shown in FIG. 3. The primary system fordetermining machine position and timing can, for example, incorporate aconventional line shaft encoder 86, which is operably connected to theprimary line shaft 88 of the apparatus. In addition, a reference signalgenerator 90 is operably connected to line shaft 88 to generate onereference pulse per each individual product section, which is intendedto be derived from fibrous web 42. The output from reference generator90 and line shaft encoder 86 are directed to a programmable controller,such as a computer, through suitable signal conduits. A conventionalinput device, such as a keyboard system 92, is employed to set variablecontrol parameters in computer 94. The computer in turn, selectivelytriggers appropriate devices, such as solid-state relays 70, to activateselected components, such as valves and actuators 104. A suitable powersupply, such as electrical power supply 60, provides the energy neededto operate the system.

In the shown embodiment, line shaft encoder 86 may be a63-P-MEF-2000-T-O-OOGH device manufactured by Dynapar Corp. located inGurnee, Ill. The encoder may, for example, be configured to generate2000 pulses per revolution.

Reference signal generator 90 may, for example, comprise a B15-G18-ANGXproximity switch manufactured by TURCH, a business located inMinneapolis, Minn. A suitable computer may, for example, comprise adevice manufactured and designated as a PME 68-23 CPU by RadstoneTechnology, a company located in Pearl River, N.Y.

In the illustrated embodiment, the pulser mechanism can be operablycontrolled by employing a reference signal generated at a predeterminedtime and position along the apparatus. For example, the reference signalmay be generated at a reference point corresponding to a machineposition at which portions of fibrous web 42 are cut away to form theleg openings of a disposable diaper. Accordingly, computer 94 can beprogrammed to trigger an actuator, such as solenoid valve 68 (FIG. 2),at the appropriate number of encoder counts after the generation of the"leg cutout" reference signal. Alternatively, the chosen reference pointmay be the "fluff cutoff" reference signal, the machine position andoperation at which fibrous web 42 is separated into individual,end-product sections.

To properly locate the particle quantity 64 along the machine directionof fibrous web 42, several other parameters should also be taken intoaccount. One parameter is the transport delay parameter, whichcorresponds to the time period between triggering the control valve 68and the arrival of the particulate quantities 64 at the foraminousforming layer 38 within the web forming chamber. The exact value of thisparameter can be readily determined by persons skilled in the art, andwill depend upon factors such as the specific dimensions of theapparatus, operating speed of the apparatus, and speed of the movingparticles.

A second parameter is the dwell time which corresponds to the timeperiod over which solenoid valve 68 remains energized. Another, optionalparameter is the "second-pulse offset" parameter which corresponds tothe delay, in encoder counts, between discrete pulses of particles whenmultiple quantities 64 are to be delivered into an appointed end-productsection of fibrous web 42. Such multiple quantities may be provided by amulti-function, single unit transferring means, or by a multiple unittransferring means. The reference to the end-product section of the webis a reference to the fact that web 42 may, for example, eventually beseparated into individual absorbent bodies or pads for use in disposablediapers. Each particular machine-direction length of web 42, whichcorresponds to an individual pad, could then be identified as anend-product section of the web.

A detecting means 96, such as a fiber optic photo-eye sensor, can bepositioned in operable proximity to delivery nozzle 36 to ascertain theabsence or presence of the individual, pulsed quantities 64.Alternatively, detecting means 96 may comprise a sensor which operateson the basis of the tribo-electric effect. For example, the sensor maybe a Model 2603 Triboflow sensor available from Auburn International,Inc. located in Danvers, Mass. End-product sections of fibrous web 42which do not receive an appropriate quantity of particles can beautomatically culled from the apparatus.

In an aspect of the invention representatively shown in FIGS. 4 and 4A,transferring means 24 (FIG. 1) can comprise a diverter system. Withregard to the illustrated embodiment of the diverter system, supplystream 18, which contains the mixture of gas and superabsorbentparticles, enters curved conduit 48 through inlet section 52, and theparticles become segregated in accumulation region 22 along the radiallyoutward wall of the conduit. At a selected position along the curvedpath of conduit 48, delivery conduit 30 is connected in operablecommunication therewith. The shown embodiment, for example, includes adelivery conduit 30 which is positioned generally tangential to curvedconduit 48. A gas supplying means provides a delivery air stream 26through delivery conduit 30, and a diverter regulator member, such asflap member 102 is positioned at the point of intercommunication betweencurved conduit 48 and delivery conduit 30. Regulator flap 102 isselectively moveable between a closed position (FIG. 4A) and an openposition (FIG. 4) by the operation of a suitable diverter actuator 104.When regulator flap 102 is in its closed position, supply stream 18 isrecirculated out of conduit 48 through outlet section 54.

When regulator flap 102 is in its open position, a metered quantity ofsuperabsorbent particles 64 can be allowed to pass from curved conduit48 into delivery conduit 30. Delivery airstream 26 can then transportthe pulsed quantity of particles to delivery nozzle 36 and formingchamber 32. As previously discussed, a phasing means is employed toselectively sequence the operation of diverter actuator 104 andregulator flap 102 to provide a desired registration between particlequantity 64 and selected deposition regions along the machine directionof web 42 (FIG. 1). In particular, computer 94 (FIG. 3) is appropriatelyprogrammed to trigger the operation of regulator flap 102 to deliver oneor more pulse quantities of particulate material into each appointedend-product section of fibrous web 42.

Particular aspects of the invention may be distinctively configured toprovide a plurality of different open positions for regulator flap 102.The regulator flap may be moveable to two or more selected, "open"positions, each of which is arranged to deliver a different flow rate ofparticulate material into delivery conduit 30. For example, regulatorflap 102 may be advantageously coupled to a servo drive system which isprogrammable to incrementally move the regulator flap to a plurality ofdifferent flap positions in accordance with a predetermined sequence. Asa result, the invention can be constructed and arranged to provide aselectively "shaped" distribution pattern of particulate material withineach individual, end-product section of web 42. The sequential,incremental movements of regulator flap 102 may, for example, beactuated by a servo drive mechanism which is operably coupled to aprogrammable control system, such as a computer, in a manner well knownin the art.

In the shown embodiment, regulator flap 102 rotates about a pivot whichis located at an "upstream" section of the flap, with the regulator flapextending generally downstream from the pivot. During operation, theflap moves to "open" positions at which the flap protrudes into deliveryconduit 30. The pivot may alternatively be located at a downstreamsection of regulator flap with the flap extending generally upstreamfrom the pivot. With such a configuration, regulator flap 102 can bearranged and structured to move to "open" positions at which the flapprotrudes into curved conduit 48.

FIG. 5 provides a more detailed illustration of web forming chamber 32.The chamber includes a fiber delivery means, such as fiberizerhammermill 34, which provides a flow of fibrous material 114 within theforming chamber. Foraminous forming layer 38, which is located informing chamber 32 and movable therein, is configured to receive adeposit of fibrous material 114 thereon. Piping means such as deliveryconduit 30 and one or more nozzles 36, supply a flow of dispersed bodiesof high absorbency material, such as superabsorbent polymer particles10. This flow of particles enters forming chambers 32 and intermixeswith the flow of fibrous material 114 therein. Regulating means, such asflow angle adjuster 126, controls a flow velocity 28 of particulatematerial 10 within the fibrous material 114 deposited onto forming layer38 to form fibrous web 42.

Forming chamber 32 includes side walls 115 and end walls which areconstructed and arranged to define a generally enclosed volume. Endwalls 116 and 118 have suitable entrance and exit openings formedtherethrough to allow the entry of forming layer 38 and the removal ofairlayed fibrous web 42 from the forming chamber.

Hammermill 34 may comprise any one of a number of types of conventionalfiberizing devices. Sheets of selected fibrous material are typicallyfed into the hammermill, and are disintegrated into a plurality ofindividual fibers 114 which are injected or otherwise introduced intochamber 32. Fibers 114 are typically composed of absorbent, woodpulpfibers commonly referred to as fluff. The fibers may also be composed ofstaple fibers, polymeric fibers, cellulosic fibers and mixtures thereof,as well as mixtures of absorbent fibers with generally hydrophobicfibers. The fibrous material may optionally be treated to impart desiredlevels of hydrophilicity, employing techniques well known in the art.

The forming apparatus of the invention may further include vacuum means132, such as a conventional blower mechanism, for creating a selectedpressure differential through forming chamber 32 and past forming layer38. The vacuum means is typically located underneath forming layer 38 tocreate an air flow through chamber 32 which is generally directed fromhammermill 34 and past forming layer 38. This airflow helps to directand control the deposit of fibers 114 and particles 10 onto the forminglayer.

Forming layer 38, for example, may comprise a foraminous forming screenconfigured as an endless belt which moves about support rollers 162 and164. A suitable driving means, such as electric motor 166, is operablyconnected to move forming layer 38 through chamber 32 at a selectedspeed along machine direction 168. Fibers 114 and particles 10 depositonto the portion of forming layer 38 within forming chamber 32 to formfibrous web 42, which eventually develops into an absorbent body 240within an absorbent article. Since forming layer 38 moves generally fromend wall 116 toward the exit opening through end wall 118, the depth orthickness of web 42 on any particular section of forming layer 38gradually increases as that forming layer section traverses through theforming chamber. The fiber deposition rate onto forming layer 38 and themovement speed of the forming layer can be suitably adjusted to controlthe finally formed thickness of the airlayed fibrous web 42.

In another aspect of the invention, forming layer 38 comprises aforaminous forming screen carrier on an outer circumferential surface ofa rotatable drum 138, as representatively shown in FIG. 6. A suitabledriving means, such as motor 167, rotates drum 138 to move forming layer38 through forming chamber 32.

The invention may include single or multiple nozzles 36 which, forexample, may comprise a conduit of circular cross-section measuringabout 5 centimeters in diameter. If desired, other regular or irregularnozzle shapes or sizes may be employed.

Referring again to FIG. 5, the nozzles may protrude into chamber 32 apredetermined distance to adjust the distribution of particulatematerial through the thickness of web 42. A larger amount of protrusioncan, for example, reduce the amount of particles deposited near theforming layer side of web 42.

Depending on the size and mass of the individual particles, thedispersed particles will tend to follow various trajectories 170-172 tointermix with the flow of fibers 114 moving through chamber 32 towardforming layer 38. Some of the particles will follow a shorter trajectory170 to deposit superabsorbent particles into web 42 at locations nearerend wall 116. Other particles will follow longer trajectories 172 todeposit into web 42 at locations closer to end wall 118. The remainderof particles will follow intermediate trajectories 171 to deposit intoweb 42 at more centrally located, intermediate regions between end walls116 and 118. Since web 42 is gradually increasing in thickness as ittraverses through chamber 32, particles 10 can be selectivelydistributed through the thickness dimension of web 42 to produce adesired concentration gradient therein.

To produce desired distribution patterns and gradients through the webthickness, an initial flow velocity 128 of the air/particle streammoving into chamber 32 can be selectively regulated by adjusting theangular direction of the flow, the height of the nozzles above forminglayer 38, and the speed of the flow. Flow regulating means comprisingblower control 158 in the shown embodiment (FIG. 1) adjusts the volumerate of gas flow into the system, and as a result, can adjust themagnitude of the mean velocity or speed of the gas/particle flow. Forexample in one embodiment of the invention, blower 28 is adjusted toprovide a mean flow velocity of the air/particle mixture which measuresat least about 5 meters/seconds. If the flow velocity is increased,relatively more particulate material can be deposited toward the upperfree surface of web 42. If the flow velocity is decreased, relativelymove particulate material can be deposited toward the forming layer sideof web 42. In a particular aspect of the invention, the flow velocity ofthe air/particle mixture is within the range of about 5-45meter/seconds.

The geometry and size of delivery nozzles 36 may be adjusted to controlthe distribution of particles along the cross-direction of theapparatus. In addition, the initial direction of the air/particle flowinto chamber 32 can be selectively changed employing angle adjustingmechanism 126, which is operated to change the angular orientation ofnozzle 36 with respect to the local horizontal direction. In aparticular aspect of the invention, angle adjusting mechanism 126comprises a rotatable connection located within delivery conduit 30. Itshould be readily apparent that angle adjusting mechanism 126 should beconfigured with a structure which does not substantially interfere withany intermittent, pulsed quantities of particles being transportedthrough the delivery conduit.

Delivery nozzles 36 can be suitably adjusted to a nonparallel angleslanted toward or away from forming layer 38. If the nozzle is angledtoward the forming layer, relatively more particulate material can bedeposited near the forming layer side of web 42. If the nozzle is angledaway from forming layer 38, relatively more particulate material can bedeposited near the upper, free surface side of web 42. For example, in aparticular aspect of the invention, nozzle 36 is constructed andarranged to be pivotable within a range of approximately plus (upwardly)45° to minus (downwardly) 60°, relative to a plane positioned generallyparallel to the forming layer. Preferably, the nozzle is pivotablewithin the range of about plus 10° and minus 45° relative to such plane,respectively away or toward the forming layer.

The entry angle of the moving superabsorbent particles can be adjustedby selectively orienting nozzle 36, and velocities of the particles canbe appropriately regulated to impart desired, predetermined trajectoriesto the particles. As a result, particular particles can travel differenthorizontal distances through chamber 32 in a direction generallyparallel to the machine direction of the apparatus. In the illustratedembodiment the particles move along with the movement of the formedfibrous web, but in alternative embodiments, the apparatus can beconfigured to move the particles counter to the movement of the fibrousweb. The difference in horizontal distances can cause differing amountsand/or differing weight percent concentrations of the particles to beselectively placed at various desired levels through the thicknessdimension of the fibrous web.

Particular aspects of the invention can include combinations of thevarious, different types systems for delivering particulate materialinto forming chamber 32. As representatively shown in FIG. 6, forexample, the invention may be configured to include a pulser-typetransferring means 24 in combination with a continuous delivery system106. The pulser-type device injects discrete, selected quantities ofsuperabsorbent particles into fibrous web 42, and continuous deliverysystem 106 provides a substantially continuous mass flow rate ofsuperabsorbent particles into the forming chamber for incorporation intothe fibrous web.

As further examples of combinations of delivery systems, FIGS. 13 and13A show a schematic representation of an embodiment of the inventionwherein the transferring means includes two pulser-type systems, andFIGS. 14 and 14A show a schematic representation of an embodimentwherein the transferring means includes a pulser-type system and adiverter-type system.

To support the operation of multiple transferring systems and deliverysystems, a flow splitting means 108, representatively shown in FIG. 8,can be employed to partition the particle/air supply stream intoseparate streams. Flow splitter 108 includes an isolating means such ascurved pipe 110, to locate particles 10 in a predictable region withinthe curved pipe. As previously discussed in the context of segregatingmeans 20, the movement of particles through pipe 110 along a curved arcconcentrates the particles toward the radially outward wall of the pipe.As a result, at the pipe outlet 112, most of the particles are flowingalong the outside wall, and the particles are directed into a dividingmechanism 120. The dividing mechanism connects to pipe outlet 112 and iscircumferentially rotatable with respect to the pipe outlet. The inletregion of the dividing mechanism is substantially circular incross-section and includes a knife member 122 located along a diameterthereof. The two major surfaces of the knife member extend axially alongthe length of the dividing mechanism. As illustrated in FIG. 8A, knifemember 122 is aligned generally along the radius of curvature of thecurved path defined by pipe 110, and extends along the radial andcircumferential directions of the pipe. As a result, knife member 122can cut the particle -stream into two portions, which are directedtoward an outlet section of dividing mechanism 120. In the illustratedembodiment, outlet section 124 branches off into a Y-configuration. Afirst particle stream is directed into a first divider arm 128 and asecond particle stream is directed into a second divider arm 130. Therelative proportion of particles directed into divider arms 128 and 130will depend upon the particular rotational position of knife member 122.Accordingly, the rotational position of knife member 122 can beselectively adjusted to direct equal or different proportional amountsof superabsorbent particles into each of the divider arms. For example,three possible rotational positions of the knife member are illustratedin FIG. 8A.

In yet another aspect of the invention, the method and apparatus mayinclude multiple transferring systems configured to deliver two or moredifferent types of particulate materials into the substrate. Forexample, one transferring mechanism may deliver particles ofsuperabsorbent material and a second transferring mechanism may deliverparticles of a non-superabsorbent material. As another example, each ofthe transferring systems may be constructed and arranged to deliver adistinctively different type of superabsorbent material. Each type ofsuperabsorbent could have a particular set of performancecharacteristics, and each type of superabsorbent could be selectivelyplaced at predetermined positions within the substrate to provide anadvantageous combination of absorbency characteristics.

A representative particle recovery system 39 is shown in more detail inFIG. 9. In the illustrated embodiment, the recovery system comprises acurved conduit 41 which includes an inlet section 43, an outlet section45 and an exhaust conduit 136. The moving, incoming gas/particulatemixture enters inlet section 43, and as the mixture moves along thearcuate path defined by the curved conduit, particles 10 becomesegregated towards the radially outward wall 51. Outlet section 45 islocated at a radially outward portion of curved conduit 41 and isconnected in operable communication with a particle reservoir section 15of feeder mechanism 14 (FIG. 1). As a result, particles 10 can bedirected through the outlet section and toward the reservoir section. Anexhaust conduit 136 is connected to outlet section 45, and the remaininggas stream is directed into exhaust conduit 136 by deflector member 49and by a pressuring means which provides a selected pressuredifferential between the gas pressure within conduit 41 and the gaspressure within reservoir 15. In particular, the reservoir static gaspressure is greater than the conduit gas pressure. As a result, therelatively high momentum of the moving particles can operably carry theparticulate material through the static pressure differential and intoreservoir 15. The gas pressure differential, however, substantiallyblocks the gas portion of the gas/particulate mixture from moving intothe reservoir. The gas portion is instead operably deflected andredirected to move through exhaust conduit 136. The deflected gas streamis substantially free of particulate material and may optionally berecirculated through appropriate conduits to provide at least a portionof delivery gas stream 26 (FIG. 1), as desired. Thus, the particulatematerial can be efficiently separated from its associated transportingstream of gas and advantageously recycled for use into reservoir 15. Theparticle recovery system of the invention can advantageously recovermore than 90% of the particles from the incoming gas/particle mixture.Particular embodiments of the recovery system can recover about 95% ofthe particles from the incoming gas/particle mixture.

With reference to FIG. 10, an integral absorbent garment article, suchas disposable diaper 210, generally delimits a front waistbandpanel-section 212, a rear waistband panel-section 214, and anintermediate section 216 which interconnects the front and rearwaistband sections. The absorbent article comprises a substantiallyfluid impermeable backsheet layer 220, a liquid permeable topsheet layer230 positioned in facing relation with backsheet layer 220, and anabsorbent body 240 is located between the backsheet layer and topsheetlayer. For reference purposes, the diaper has a longitudinal direction142, a cross-direction 144 and a longitudinal centerline 146.

Marginal portions of diaper 210, such as marginal sections of backsheet220, may extend past the terminal edges of absorbent body 240. In theillustrated embodiment, for example, backsheet 220 extends outwardlybeyond the terminal marginal edges of absorbent body 240 to form garmentside margins 226 and 228 and garment end margins 222 and 224. Topsheet230 is generally coextensive with backsheet 220, but may optionallycover an area which is larger or smaller than the area of backsheet 220,as desired.

Diaper 210 may be of various suitable shapes. For example, the diapermay have an overall rectangular shape, T-shape or an approximatelyhour-glass shape. In the shown embodiment, diaper 210 has a generallyI-shape.

The various components of diaper 210 are integrally assembled togetheremploying various types of suitable attachment means, such as adhesive,sonic bonds, thermal bonds, and the like, and combinations thereof. Inthe shown embodiment, for example, topsheet 230 and backsheet 220 areassembled to each other and to absorbent body 240 with lines andpatterns of adhesive, such as a hot melt, pressure-sensitive adhesive.Similarly, other diaper components, such as elastic members 260 and 264and fastening members 236, may be assembled into the diaper article byemploying the above-identified attachment mechanisms.

The illustrated embodiment of diaper 210 includes ear portions 248,which extend laterally along the diaper cross-direction 144 and arepositioned at least at one waistband section of diaper 210, preferablyat the rear waistband section 214. Ear portions 248 may also be locatedat front waistband section 212 of the diaper. The ear portions may beintegral with backsheet layer 220, or may comprise separate sections,which are composed of the same or different material than backsheet 220and are suitably assembled and attached to the backsheet layer. Earsections 248 typically provide extensions of the diaper waistbandsuitable for completely encircling the waist of the wearer during use.

Fastening means, such as adhesive tapes 236, are employed to secure thediaper on a wearer. Alternatively, other fastening means, such asbuttons, pins, snaps, hook-and-loop fasteners, mushroom-and-loopfasteners, or the like, may be employed.

To provide improved fit and to help reduce leakage of body exudates fromdiaper 210, the diaper side margins and end margins may be elasticizedwith suitable elastic members, such as single or multiple strands ofelastic. The elastic strands may be composed of natural or syntheticrubber, and may optionally be heat-shrinkable or heat-elasticizable.Elastic members 260 and 262 are constructed to operably gather and shirrside margins 226 and 228 to provide elasticized leg bands which canclosely fit around the legs of the wearer to reduce leakage and provideimproved comfort and appearance. Similarly, waist elastic members 264and 266 can be employed to elasticize diaper end margins 222 and 224 toprovide elasticized waistbands. The waist elastics are configured tooperably gather and shirr the waistband sections to provide a resilient,comfortably close fit around the waist of the wearer.

Backsheet 220 is composed of a substantially liquid impermeablematerial, which is also gas impermeable but may optionally be gas/vaporpermeable. In the illustrated embodiment, the backsheet is substantiallyimpermeable to water and water vapor. An example of a suitable backsheetmaterial is a polymer film composed of polyethylene, polypropylene, orthe like. Typically, the polymer film has a thickness within the rangeof about 0.0007-0.002 inch (0.0018-0.0051 cm). Backsheet 220 mayalternatively be composed of a nonwoven fibrous web constructed toprovide the desired levels of fluid impermeability. For example webcomposed of spunbonded or meltblown polymer fibers may be selectivelytreated with a water repellent coating, or laminated with a fluidimpermeable, polymer film.

In alternative embodiments of the invention, backsheet 220 may comprisea nonwoven web composed of a plurality of randomly deposited hydrophobicthermoplastic meltblown fibers which are sufficiently bonded orotherwise connected to one another to provide a substantially vaporimpermeable and substantially liquid impermeable web. The backsheet mayalso comprise a vapor permeable nonwoven layer which has been partiallycoated or otherwise configured to provide liquid impermeability only inselected areas, leaving the remaining areas vapor permeable.

Topsheet 230 is typically composed of a liquid permeable, substantiallyhydrophobic fibrous material, such as a spunbonded web composed ofsynthetic polymer filaments. Alternatively, topsheet 30 may comprise ameltblown web or a bonded-carded-web composed of synthetic polymerfilaments. Suitable synthetic polymers include, for example,polyethylene, polypropylene and polyesters. In a particular aspect ofthe invention, the polymer filaments have a denier within the range ofabout 1.5-7d and preferably have a denier within the range of about1.5-3d to provide improved performance. The filaments are arranged toform a layer having a basis weight within the range of about 8/-34 gm/m²(gsm), and preferably are arranged to have a basis weight of about 27gsm. In addition, the topsheet layer has a bulk thickness within therange of about 0.008-0.017 inches (about 0.0203-0.0432 cm), andpreferably has a bulk thickness within the range of about 0.010-0.12inches (about 0.0254-0.305 cm) for improved effectiveness. The bulkthickness is measured under a restaining pressure of 0.014 psi (0.096kPa).

Topsheet 230 may optionally be treated with surfactants to adjust itsdegree of hydrophobicity and wettability. It can also be selectivelyembossed or apertured with discrete slits or holes 232 extendingtherethrough.

Absorbent body 240 comprises an integral mass of hydrophilic materialwhich is typically configured to form a fibrous absorbent pad layer. Thehydrophilic fibers can, for example, be composed of a fibrous cellulosicmaterial commonly referred to as woodpulp fluff, and can be airlaid toform an integral fibrous pad. Other fibers, such as cotton and syntheticpolymer fibers, may also be employed to form the pad. Conventionalabsorbent pads can have a density ranging from about 0.05-0.20 grams/cc,and are sufficiently flexible to readily conform to the body shape ofthe wearer. In particular arrangements, the fibrous material comprisingthe pad may be nonuniformly distributed over the pad length and width.For example, see U.S. Pat. No. 4,585,448, "Disposable Garment HavingHigh-Absorbency Area", issued Apr. 29, 1986 to K. Enloe.

Absorbent body 240 may alternatively include an integral layer of afibrous coform material composed of a mixture of cellulosic fibers andsynthetic polymer fibers. For example, the coform material may becomposed of an airlaid blend of cellulosic fibers and meltblownpolyolefin fibers, such as polyethylene and/or polypropylene fibers. Inone aspect of the invention, the fibrous material comprising absorbentbody 240 is composed of filaments having a coarseness of about 10-20mg/100 meters, and preferably having a coarseness within the range ofabout 10-18 mg/100 meters. The filaments are arranged to form a layerhaving a basis weight within the range of about 400-1200 gsm, andpreferably having a basis weight of about 800 gsm. In addition, theabsorbent body material typically has a bulk thickness within the rangeof about 0.17-0.21 inches (about 0.432-0.533 cm), as measured under arestraining pressure of 0.068 psi (0.47 kPa).

To increase the absorbent capacity of absorbent body 240, it has beendesireable to add quantities of relatively high-absorbency material tothe fibers comprising the absorbent body. Such high-absorbency materialsare capable of holding, on a weight basis, at least about 15 parts ofwater per part of high-absorbency material. Preferably, the highabsorbency material is capable of holding at least about 50 parts ofwater per part of high-absorbency material.

Absorbent body 240 should include an effective amount of thehigh-absorbency material to operably enhance the absorptive capacity ofthe absorbent body. For example, absorbent body 240 can contain 5-95weight percent high-absorbency material, and preferably includes about10-30 weight percent of the high-absorbency material to provide moreefficient performance.

The high-absorbency material has typically been distributed or otherwiseincorporated into absorbent body 240 by employing various techniques.For example, the high-absorbency material can be incorporated into aseparate carrier sheet which is layered with a body of airlaidcellulosic fibers. Alternatively, the high-absorbency material may besubstantially uniformly distributed and mixed within the mass of fiberscomprising the absorbent body. The material can also be non-uniformlydistributed among the fibers to form, for example, a generallycontinuous gradient with either an increasing or decreasingconcentration of high-absorbency material, as determined by observingthe concentration moving from the body-side of absorbent body 240 towardthe outer-side of the absorbent body. The high-absorbency material mayalso be substantially unmixed with the fibrous material of absorbentbody 240, and may comprise one or more discrete layers or stripsselectively segregated from the fibrous material.

Optionally, a substantially hydrophilic tissue wrap 242 may be employedto help maintain the integrity of the airlaid fibrous structure ofabsorbent body 240. The tissue wrap sheet is typically placed about theabsorbent body over at least the two major facing surfaces thereof, andcomposed of an absorbent cellulosic material, such as creped wadding ora high wet-strength tissue.

In the article aspect of the invention, absorbent body 240 has thestructural configuration of a concurrently airlaid mixture ofhydrophilic fibers and superabsorbent particles. The fibers andparticles are concurrently formed into a substantially integral weblayer while the fibers and particles are non-homogeneously intermingledwith each other. In such structure, the superabsorbent particles are notsubstantially isolated in a discrete superabsorbent layer. The resultantabsorbent body can include a distinctive, selectively varieddistribution of superabsorbent particles along the longitudinal lengthdimension 142 of the absorbent body. For example, the average weightpercentage of superabsorbent particles can be nonuniformly distributedalong said length dimension.

It is recognized that there may also be some variations in theconcentration of superabsorbent particles along the cross-direction 144of absorbent body 240. Accordingly, for the purposes of the presentinvention, the distribution of superabsorbent particles should beconsidered in the context of a representative, functional region locatedsubstantially along and about the longitudinal center line 146 of theabsorbent body. It will be appreciated that the particular dimensionsand shape of the functional region will depend upon the intended use,and the size and configuration of the overall absorbent body. Thesuperabsorbent concentration at a particular, chosen location along thelength of the absorbent body will be an average concentration taken overthe cross-directional width of the absorbent body at that location.

The intermixed configuration of the superabsorbent particles and fibrousmaterial is desireable because it can provide an advantageouscombination of capillarity, interfiber void volume and total absorbentcapacity. The fibrous material contributes to the capillarity andinterfiber void volume, while the superabsorbent particles contribute tothe total absorbent capacity. The fiber capillarity helps provide arapid movement and wicking of liquid through the absorbent body and theinterfiber void volume helps provide a rapid rate of liquid uptake intothe absorbent body. In addition, the intermingled configuration of theparticles and fibrous material helps improve the mechanical integrity ofthe total structure.

As representatively shown in the graph of FIG. 11A, absorbent body 240can advantageously include a nonuniform distribution of superabsorbentparticles having the arrangement of a substantially continuous gradientof concentrations along longitudinal length dimension 142. In theillustrated embodiment, the superabsorbent concentration gradientcontinuously increases and decreases in a non-step-wise arrangement. Theparticles are selectively arranged in an airlaid, dispersed structure toprovide a distinctive, non-homogeneous mixture within the substantiallyintegral fibrous layer comprising the absorbent body. The particles arein a non-layered configuration, and are not substantially isolatedwithin a discrete layered zone wherein the particles are substantiallyunmixed with fibrous material.

While the absorbent body may or may not include absorbent particlesalong its total length, the present invention can advantageously providea configuration of the absorbent body wherein a greater amount ofparticles are located at selected positions along the length of theabsorbent body and wherein the particles are substantiallynon-homogeneously mixed within the associated, intermingled quantity offibrous material located at those selected positions. Accordingly, agreater (or smaller) proportion of superabsorbent particles may belocated at the selected positions along the length of the absorbent bodywithout also locating a corresponding, greater (or smaller) proportionof the fibrous material at those selected positions. In particularaspects of the invention, a greater proportion of superabsorbentparticles may be located at the selected, length-wise positions of theabsorbent body without also locating a corresponding, greater basisweight (weight per unit area) of the fibrous material at those selectedpositions. Conversely, a lesser proportion of superabsorbent particlesmay be located at selected positions along the length of the absorbentbody without also locating a corresponding, smaller basis weight (weightper unit area) of fibrous material at those selected positions.

Thus, the concentration of superabsorbent particles at a particularlocation may be configured to be substantially independent of the amount(e.g. basis weight) of fibrous material at that location. When oneobserves different contiguous sections taken from along the length ofthe absorbent body, the amount of particulate material does not rise andfall in a substantially direct correspondence with a rise and fall ofthe amount of fibrous material in those sections. A particularembodiment of the invention, for example, can comprise an arrangementwherein the local amount of particulate material does not rise and fallin correspondence with a rise and fall of the local basis weight (weightper unit area) of the fibrous material in that section. Otherembodiments can similarly be configured wherein the weight percentage ofthe total amount of superabsorbent or the weight of superabsorbent perunit area is nonuniformly distributed along the length of the article ina substantially continuous distribution profile, but does not change(rise and/or fall) in a substantially direct correspondence with thelength-wise change in the local basis weight or local weight-percentagelevel of the associated fibrous material.

In a preferred embodiment, a greater proportion of superabsorbentparticles may be concentrated toward at least one longitudinal end ofthe absorbent body without a corresponding greater proportion (e.g.basis weight) of the fibrous material also being concentrated at thatend of the absorbent body. In a more specific embodiment, the particlescan be concentrated toward the front waistband end 148 of the absorbentbody. As a result, the superabsorbent can be more efficiently located inthose regions which typically are more heavily wetted by the wearer, andlesser amounts of superabsorbent material can be located in thoseregions which typically receive lesser amounts of liquid. The effectivelevel of total absorbency of the absorbent body can thereby be improvedor maintained while using the same or lesser amounts of the relativelyexpensive superabsorbent material.

In particular aspects of the invention, at least about 50 wt% and notmore than about 95 wt% of the total amount of superabsorbent particlesare located in the front 50% of the overall length of absorbent body240. Preferably, about 55-85 wt% and more preferably, about 60-85 wt% ofthe total amount of superabsorbent particles are located in the front50% of the overall absorbent body length. Such weight percentages ofsuperabsorbent, however, are not present in combination withcorresponding, similar weight percentages of the total amount of fibrousmaterial. For example, the front 50% of the length of absorbent body 240may include 60-80 wt% of the total amount of superabsorbent but onlyinclude 55 wt% of the total amount of fibrous, fluff material. Asanother example, the front 50% of the absorbent body may include 60-80wt% of the total amount of superabsorbent, but only include 40-50 wt% ofthe total amount of fibrous material.

In further embodiments of the invention, relatively higher weightpercentages of the superabsorbent material can be selectively located atpredetermined locations along the length of absorbent body 240. Forexample, 50-60 wt% of the total amount of fibrous material may belocated in a front 45% of the absorbent body while 50-80 wt% of thetotal amount of superabsorbent is located in a middle 30% of theabsorbent body. Thus, the region having the maximum weight percentage ofintermixed fibrous material can be offset lengthwise from the regionhaving the maximum weight percentage of intermixed superabsorbentmaterial.

The article aspect of the invention can advantageously be constructed toprovide a distinctive absorbent body comprising a plurality of two ormore different types of superabsorbent material, with each typecharacterized by it own predetermined set of functional parameters. Forexample, different types of superabsorbent materials can have differentvalues for shear modulus, grams of liquid absorbed per gram ofsuperabsorbent material, rate of absorption of liquid, gel strength,ability to swell under compressive load, cost etc.. As a result,particular types of different superabsorbents can be selectively chosento provide a desired combination of functional characteristics which maynot be available from a single type of superabsorbent material. Inaddition, the different types of superabsorbent material may beselectively positioned along the length, width or thickness of theabsorbent body to more effectively take advantage of the particularcharacteristics afforded by each type of superabsorbent.

Referring now to FIG. 11A, a representative pulsing system of theinvention (FIG. 11) can advantageously produce along the length ofabsorbent body 240 a particle distribution having the general shape ofan inverted spoon. The particle distribution provides a substantiallycontinuous, non-step-wise gradient of particulate concentrations. Thegradient is generally aligned and extends along the length of theabsorbent body. The substantially continuous distribution profile has abowl section 250 which represents major concentrations of relativelylarger amounts of particles and a handle section 252 which representsthe lesser concentrations or amounts of particles. Beginning at thefront waistband edge of absorbent body 240, the weight percent ofsuperabsorbent particles, determined with respect to a selected totalamount of superabsorbent within absorbent body 240, is less than about30 weight percent. Preferably, the proportion of superabsorbentparticles is less than about 20 wt%, and more preferably is less thanabout 10 wt%. The weight percentage of particles gradually rises in the"increasing" section 254 of the distribution profile until it reaches amaximum at a location within the range of approximately 5-30% of thetotal length of the absorbent body. The maximum, peak proportionalamount of superabsorbent particles is typically not more than about 40wt%. After reaching the peak weight percent, the concentration ofsuperabsorbent particles gradually falls in the "decreasing" section 256of the profile until it reaches a value of less than about 30 weightpercent at a region positioned at about 40-90% of the absorbent bodylength away from the front waistband edge. Preferably, the proportion ofsuperabsorbent particles is less than about 20 wt% and more preferablyis less than about 8 wt% within this region of the absorbent body.

FIG. 12A representatively shows a particle distribution produced by theembodiment of the invention (FIG. 12) which includes a diverter-typesystem for producing intermittent particle flows. The diverter-typesystem can advantageously produce along the length of absorbent body 240a substantially continuous particle distribution having the generalshape of a plateau. The particle distribution has an "increasing"section 270 in which the superabsorbent concentrations are rapidlyrising, a plateau section 272 in which the maximum superabsorbentconcentrations remain substantially constant, and a "decreasing" section274 in which the superabsorbent concentrations are rapidly falling.Beginning at the front waistband edge of absorbent body 240, the weightpercent of superabsorbent particles, determined with respect to a unitweight of absorbent body 240, is less than about 25 weight percent.Preferably, the proportion of superabsorbent particles is less thanabout 20 wt%, and more preferably is less than about 10 wt%. The weightpercentage of particles gradually increases until it reaches a plateaumaximum at a location within the range of approximately 5-30% of thetotal length of the absorbent body. The proportional amounts ofsuperabsorbent particles along the plateau section of the distributionare typically not more than about 40 wt%. After reaching the end of theplateau section, the concentration of superabsorbent particles decreasesin the "falling" region of the distribution until it becomes less thanabout 30 weight percent at a region positioned at about 40-90% of theabsorbent body length away from the front waistband edge thereof.Preferably, the concentration of superabsorbent particles decreases to alevel which is less than about 20 wt%, and more preferably decreases toa level which is less than about 8 wt%.

The distribution of superabsorbent particles within the absorbent bodymay also be distinctively configured with two or more stages. FIG. 13A,for example, representatively shows a superabsorbent particledistribution produced by an embodiment of the invention which includes acombination of two pulsing systems (FIG. 13). The two pulser-typesystems may deliver the same type or different types of superabsorbentmaterial. In the illustrated embodiment, the first quantity ofsuperabsorbent particles provided by the first pulser mechanism(distribution profile 255) is positioned relatively closer to the frontwaistband end of the absorbent article, and the second quantity ofsuperabsorbent particles delivered by the second pulser mechanism(distribution profile 257) is positioned relatively closer to the backwaistband end of the article. Accordingly, the two types ofsuperabsorbent have different positional arrangements along the lengthdimension of the article. The illustrated arrangement includes aselected amount of overlap between the first and second quantities ofsuperabsorbent within the single, integral layer of absorbent fibers. Asa result, there is a distinctive step-wise, "stacked" change in theoverall, composite superabsorbent distribution 259 along the lengthdimension of the article, and the distribution is in part distinguishedby at least two discrete, interconnected stages in the "increasing"segment 253 of the composite superabsorbent distribution.

FIG. 14A representatively shows a particle distribution produced by anembodiment of the invention which includes, in combination, apulser-type system and a diverter-type system (FIG. 14). Such acombination-type system can advantageously produce an absorbent bodyhaving a combination of the spoon-shaped, superabsorbent distributionprofile 258 and plateau-shaped distribution profile 278. The combinationsystem can also be configured to deliver different types ofsuperabsorbent into the formation of the absorbent body. The shownembodiment of this arrangement includes a superabsorbent distributionwherein a first quantity of particulate material provided by thepulser-type system is arranged in the spoon-shaped section 258 of thedistribution. The spoon-shaped section is offset towards the frontwaistband edge of the absorbent body, and overlaps with theplateau-shaped section 278 of the superabsorbent distribution producedby a second quantity of particulate material provided by thediverter-type system. As a result, there is a distinctive step-wise,"stacked" change in the overall, composite superabsorbent distributionalong the length dimension of the article, and the compositedistribution 280 is in part distinguished by at least two discretestages in the "decreasing" segments 282 of the composite superabsorbentdistribution. In alternative arrangements of this aspect of theinvention, the relative positions and degree of overlap of the first andsecond quantities of particulate material may be changed. Accordingly,there may be two or more discrete stages in either or both of the"increasing" and "decreasing" segments of the composite superabsorbentdistribution.

FIG. 15B representatively shows a particle distribution produced by anembodiment of the invention which includes a multiple-position,diverter-type system (FIG. 15 and 15A). Such a system can advantageouslyproduce an absorbent body having a combination of two or moreinterconnected plateau-shaped superabsorbent distributions, which aresequentially located contiguous with each other. The shown embodiment ofthe absorbent body is distinguished by a superabsorbent distribution(FIG. 15B) wherein a first quantity of particulate material is arrangedin a first, base section 273 of the distribution, a second quantity ofparticulate material is arranged in a second, serially located plateausection 274 of the distribution and a third quantity of particulatematerial is arranged in a third, serially located plateau section 277 ofthe distribution. The first quantity of particulate material is providedwhen the diverter-type system is at a first, closed position while abase distribution is being delivered into the absorbent body byconventional means (not shown). The second quantity of particulatematerial is provided when the diverter-type system is actuated to asecond partially open position (FIG. 15A (2)) to produce a plateau inthe distribution having a first plateau value in section 274. The secondquantity of particulate material is provided when the diverter-typesystem is actuated to a third, fully open position (FIG. 15A at (3)) toproduce a plateau in the distribution having a second, maximum plateauvalue in section 277. Since the three contiguous and interconnectedsections of the composite distribution have different characteristicvalues for the concentrations of particulate material, there is adistinctive step-wise change in the overall, composite superabsorbentdistribution along the length dimension of the article, and thecomposite distribution 286 is in part distinguished by at least twodiscrete stages in the "increasing" segments 288 of the compositeparticulate distribution. In alternative arrangements of this aspect ofthe invention, the relative maximum values and the relative sequentialrelationships of the individual plateau sections material may bechanged. Accordingly, there may be two or more discrete stages in eitheror both of the "increasing" and "decreasing" segments of the compositeparticulate distribution.

FIG. 16 representatively shows an alternative particle distributionwhich can be produced with a combination system or with a multipleposition, diverter-type system of the present invention. In theillustrated embodiment, the superabsorbent distribution has adistinctive "bilobal" shape with relatively greater amounts ofsuperabsorbent at the front and rear waistband ends of the absorbentlayer and with relatively smaller amounts of superabsorbent at theintermediate section of the absorbent layer. Accordingly, the graphicrepresentation of the superabsorbent distribution increases in twodiscrete stages, but the step-wise stages are "unstacked" and areserially and separately positioned in discrete, spaced relation alongthe length of the absorbent layer. In the shown embodiment, theproportional amounts of superabsorbent at the various measured locationsalong the length of the absorbent layer are determined in terms ofweight percentage of the total amount of superabsorbent contained withinthe overall region of the absorbent body taken for analysis andmeasurement.

The following examples are provided to afford a more detailedunderstanding of the invention. The particular materials, proportionsand other parameters are exemplary and are not intended to specificallylimit the scope of the invention.

EXAMPLE 1

Disposable diapers were constructed in accordance with the presentinvention. Each of the diapers included an absorbent body comprising anon-homogeneous mixture of cellulosic woodpulp fluff and superabsorbentparticles composed of a sodium polyacrylate superabsorbent hydrogelmaterial (SAM). In the manufacture of the diapers, the fibrous woodpulpfluff and superabsorbent particles were concurrently airlaid to form anintegral fibrous web, and a diverter-type system was employed to deliverthe superabsorbent particles into the airlaying process. The airlaid webwas wrapped with a high wet-strength cellulosic tissue wrap, and thewrapped web was separated and shaped into individual absorbent bodies,commonly referred to as absorbent pads. The pads were used tomanufacture disposable diapers. The basis weight of the fluff within thepads was nonuniform, ranging between approximately 380-830 gm/m², withthe higher basis weight regions positioned towards the front waistbandedge of the pads. The pads had an overall, I-shape with a longitudinallength of about 15 inches (about 38.1 cm).

For the purpose of determining the superabsorbent distribution profile,test sections were cut from ten substantially identical diaper pads.Each test section was taken from a pad region centered about the diaperlongitudinal centerline. Each pad test section, which measured 15 incheslong and 5.5 inches wide, was then cut into 15 individual, numbered testsamples (#1-#15), each of which measured 1 inch by 5.5 inches.Accordingly, there was a group of ten #1-samples, a group of ten#2-samples, a group of ten #3-samples and so on, thereby providing 15sample groups. The average weight of superabsorbent per numbered samplefor each of the 15 groups was then determined. After determining theaverage total weight of superabsorbent for an individual, entire testsection, the average weight percentage per numbered sample (averagedover the 10 samples in the corresponding sample group) was calculated.The resultant data were employed to plot the graph representativelyshown in FIGS. 17 and 17A.

Various conventional techniques may be employed to determine thequantitative amount of superabsorbent material within a test sample.Suitable analytical techniques include, for example, a sulfated ashmeasurement method, such as described in Vogel's Textbook ofQuantitative Inorganic Analysis, Fourth edition, revised by J. Bassett,R. C. Denney, G. H. Jeffery, J. Mendham, Longman Inc., 1978, pp.479-481. Another suitable technique would be an ion exchange method(e.g. sodium ion exchange), such as described in Treatise on AnalyticalChemistry, Volume 1, edited by I. M. Kolthoff and Phillip J. Elving,Interscience Publishers, Inc., 1961, pp. 345-350. Further suitabletechniques include atomic absorption methods, such as described inVogel's Textbook of Quantitative Inorganic Analysis, Fourth edition,revised by J. Bassett, R. C. Denney, G. H. Jeffery, J. Mendham, LongmanInc., 1978, pp. 810-845. The Encyclopedia of Industrial ChemicalAnalysis, Volume 18, edited by Foster Dee Snell and Leslie S. Ettre,Interscience Publishers, Inc., division of John Wiley & Sons, 1973, atpp. 207-259 further describes well known, conventional techniques forquantitatively measuring the amount of sodium within a sample.

In the analyses conducted for the purposes of the present Examples, thequantitative determinations were made by an ion exchange method. Sincethe chemical compositions of the superabsorbent polymers employed in theExamples included particular, known proportions of sodium, a sodiumselective ion detection method was employed. This technique measured thequantitative amounts of sodium and then employed the resultantmeasurements to derive the associated, corresponding amounts ofsuperabsorbent polymer.

In particular, the test samples of absorbent pad undergoing quantitativeanalysis were intimately and completely mixed in a mixing container witha solution containing a suitable exchange ion, such as ions ofpotassium, calcium, lithium or ammonium. The solution was sufficientlyconcentrated to force the sodium out of the superabsorbent polymer andinto the solution. For the analyses of the present Examples, thesolution contained about a 0.3 molar concentration of the exchange ion,and approximately 30 ml of solution was mixed per gram of pad material.

After a thorough mixing of the sample pad material in the solution, asodium specific electrode was employed to detect the amount of sodiumions in the resultant, mixed solution. The output from the electrode wasprocessed by an ion analyzing electrode meter. A suitable electrode is aROSS™ Sodium Electrode, Model 84-11, and a suitable ion analyzer is anORION pH/ISE meter, Model EA-940. Each of these devices is availablefrom Orion Research, Inc., a business having offices at Schrafft Centerin Boston, Mass. The electrode was appropriately calibrated employing"known" standard solutions, in accordance with its associatedinstruction manual. The standard solutions were composed of ion exchangesolutions which had been mixed with specific, known amounts of theparticular superabsorbent material contained in the pads, and at leastthree different standard solutions were used to calibrate the electrode.The electrode meter was appropriately programmed/calibrated to provide aread-out in terms of grams of superabsorbent. The programming procedurewas described in the instruction manual provided with the device.

It will be readily appreciated that articles made in accordance with thepresent invention may contain superabsorbent materials having chemicalcompositions different than that of the superabsorbent employed in theExamples. Such different superabsorbents may not contain sodium butwould contain some other characteristic chemical component. Accordingly,the selected analytical technique for quantitatively measuring theamount of superabsorbent may need to be adjusted to target theparticular, characteristic component present in those compositions. Themanner of such adjustment would be readily apparent to persons ofordinary skill in the analytical arts.

For comparison purposes, pads from a conventional diaper product wereanalyzed in accordance with the technique employed in this Example 1.Referring to FIG. 18 which graphically represents the relative amountsof superabsorbent and fibrous fluff along the length of the conventionaldiaper, it can be seen that on the average the particles ofsuperabsorbent were substantially uniformly distributed along the lengthof the conventional diaper pad.

EXAMPLE 2

Disposable diapers are constructed in accordance with Example 1. Each ofthe diapers includes an absorbent body comprising a nonhomogeneousmixture of cellulosic woodpulp fluff and superabsorbent particlescomposed of sodium polyacrylate superabsorbent hydrogel material (SAM).Test sections of the diapers are analyzed in accordance with Example 1and exhibit the relative amounts of fluff and superabsorbent materialgraphically represented in FIGS. 19 and 19A. In these diapers, theregions of increased levels of superabsorbent are substantially "inphase" with the regions of increased levels of fluff.

Additional diapers are constructed and analyzed in accordance with thisExample 2. Test sections of the diapers exhibit the relative amounts offluff and superabsorbent material graphically represented in FIG. 19B.In these diapers, the regions having increased levels of superabsorbentare "out of phase" with the regions having increased levels of fluff.The amount of the "out of phase" offset is about three inches.

EXAMPLE 3

Disposable diapers are constructed in accordance with Example 1. Each ofthe diapers includes an absorbent body comprising a nonhomogeneousmixture of cellulosic woodpulp fluff and superabsorbent particlescomposed of sodium polyacrylate superabsorbent hydrogel material (SAM).Test sections of the diapers are analyzed in accordance with Example 1and exhibit the relative amounts of fluff and superabsorbent materialgraphically represented in FIG. 20 and 20A. In this Example, the regionshaving increased levels of superabsorbent are "out of phase" with theregions having increased levels of fluff by approximately six inches,and are offset towards the rear waistband section of the diaper.

EXAMPLE 4

Disposable diapers are constructed in accordance with Example 1. Each ofthe diapers includes an absorbent body comprising a nonhomogeneousmixture of cellulosic woodpulp fluff and superabsorbent particlescomposed of sodium polyacrylate superabsorbent hydrogel material (SAM).Test sections of the diapers are analyzed in accordance with Example 1and exhibit the relative amounts of fluff and superabsorbent materialgraphically represented in FIG. 21. In this Example, the regions ofincreased levels of superabsorbent are "out of phase" with the regionsof increased levels of fluff by approximately nine inches and arefurther offset towards the rear waistband section of the diaper.

Having thus described the invention in rather full detail, it will bereadily apparent to a person having ordinary skill in the art thatvarious changes and modifications can be made without departing from thespirit of the invention. All of such changes and modifications arecontemplated as being within the scope of the present invention, asdefined by the subjoined claims.

We claim:
 1. A method for forming a zoned distribution of particulatematerial within a fibrous web, comprising the steps of:(a) providing agas entrained supply stream of said particulate material; (b)segregating at least a portion of said particulate material into anaccumulation region by centrifugally directing said portion ofparticulate material into said accumulation region; (c) selectivelytransferring particulate material from said accumulation region into adelivery gas stream to provide an intermittent flow of a selectedquantity of particulate material from said accumulation region through adelivery conduit and into a web forming chamber; (d) providing a flow ofa selected fibrous material into said web forming chamber; (e)controlling said intermittent flow of particulate material from saiddelivery conduit into said forming chamber; and (f) receiving saidfibrous material and said particulate material on a foraminous forminglayer located within said forming chamber to produce a fibrous web whichincludes zoned regions having selected, different amounts of saidparticulate material therein.
 2. A method as recited in claim 1, whereinsaid segregating step (b) includes the steps ofdirecting saidparticulate material through a curved conduit having an arcuate bendthrough which said supply stream moves to operatively concentrate saidparticulate material toward to radially outward wall of said curvedconduit; and controlling a velocity of flow of said particulate materialwith said supply stream.
 3. A method as recited in claim 2, wherein saidcurved conduit provides a path having a radius of curvature within therange of about 0.05-5.0 m, as measured to said radially outward wall ofthe conduit.
 4. A method as recited in claim 3, further comprising thestep of detecting said intermittent flow of particulate material fromsaid delivery conduit into said forming chamber to ascertain a presenceor absence of individual quantities of said particulate material.
 5. Amethod as recited in claim 3, wherein said providing step (a) includesthe steps of:generating a stream of conveying gas for entraining saidparticulate material; and regulating a flow of said conveying gas toprovide a gas flow velocity within the range of about 5-45 m/sec.
 6. Amethod as recited in claim 5, further comprising the steps of:providingsaid delivery gas stream; and regulating a flow of said delivery gasstream to provide a velocity of gas flow within the range of about 5-45m/sec.
 7. A method as recited in claim 6, further comprising the step ofproviding a selected, regulated mass flow rate of particulate materialwithin said supply stream.
 8. A method as recited in claim 7, furthercomprising the step of recovering a portion of said particulatematerial.
 9. A method as recited in claim 1, wherein said selectivetransferring step (c) comprises the steps of:intermittently divertingsaid particulate material over a selected dwell time period to deliver acontrolled quantity of said particulate material from said accumulationregion into said delivery conduit; and providing said delivery stream ofgas at a selected velocity to move said quantity of particulate materialthrough said delivery conduit.
 10. A method as recited in claim 1,wherein said selective transferring step (c) comprises the stepsof:diverting said particulate material over a selected dwell time periodwith an intermittently movable flap member to deliver a controlledquantity of said particulate material from said accumulation region intosaid delivery conduit; and providing said delivery stream of gas at aselected velocity to move said quantity of particulate material throughsaid delivery conduit.
 11. A method as recited in claim 1, wherein saidselective transferring step (c) comprises the steps of:diverting aselected quantity of said particulate material from said accumulationregion into a receiving chamber; and selectively controlling saiddelivery stream of gas to intermittently move said quantity ofparticulate material from said receiving chamber and into said deliveryconduit;
 12. A method as recited in claim 11, further comprising thestep of directing a substantially continuous stream of particulatematerial into said web forming chamber.
 13. A method as recited in claim1, further comprising the step of directing a substantially continuousstream of particulate material into said web forming chamber.
 14. Amethod as recited in claim 1, wherein said selective transferring step(c) comprises the steps of:directing a first particulate material intosaid web forming chamber with a first transferring means; and directingat least a second particulate material into said web forming chamberwith a second transferring means.
 15. A method as recited in claim 14,further comprising the step of directing a substantially continuousstream of particulate material into said web forming chamber.
 16. Amethod as recited in claim 1, further comprising the step dividing saidsupply stream of particulate material into two or more substantiallyseparate, supply substreams of particulate material.
 17. A method asrecited in claim 16, wherein said step of dividing said supply stream ofparticulate material comprises the steps of:moving said gas entrainedsupply stream of particulate material through a curved conduit having aradiused bend to concentrate said particulate material toward a radiallyoutwardly positioned, interior wall member of said curved conduit; anddividing said concentrated particulate material with a separating vanemember located within an exit zone from said curved conduit and arrangedto extend along a line which substantially traverses the cross-sectionof said conduit exit zone, with the major surfaces of said vane membersubstantially aligned along a longitudinal dimensions of said conduitexit zone, said vane member being selectively positionable within saidconduit exit zone to divide said concentrated particulate material intosaid supply substreams.
 18. A method as recited in claim 17, whereinsaid conduit exit zone has a substantially circular cross-section andsaid vane member is circumferentially rotatable to provide selectivepositionability within said conduit exit zone.
 19. A method as recitedin claim 16, further comprising the steps of:directing a first substreamof the particulate material through a delivery conduit into said webforming chamber; and directing a second substream of the particulatematerial to a segregating means.
 20. A method as recited in claim 16,wherein a first substream of the particulate material is directed to afirst segregating means, and a second substream of the particulatematerial is directed to a second segregating means.
 21. A method asrecited in claim 20, wherein each of said first and second segregatingmeans comprises:a curved conduit having an arcuate bend through which acorresponding substream of particulate material moves to operativelyconcentrate gas entrained particulate material toward a radiallyoutwardly located wall of said curved conduit; and means for controllinga flow velocity of said particulate material within each substream ofparticulate material.
 22. A method as recited in claim 21, furthercomprising the steps of:selectively diverting said particulate materialover a selected dwell time period to intermittently deliver a firstquantity of said particulate material from said curved conduit of saidfirst segregating means and into a delivery conduit; and providing adelivery stream of gas at a selected flow velocity for moving saidquantity of particulate material through said delivery conduit.
 23. Amethod as recited in claim 21, further comprising the stepsof:selectively diverting said particulate material over a selected dwelltime period with an intermittently movable flap member to intermittentlydeliver a first quantity of said particulate material from said curvedconduit of said first segregating means and into a delivery conduit; andproviding a delivery stream of gas at a selected flow velocity formoving said quantity of particulate material through said deliveryconduit.
 24. A method as recited in claim 23, further comprising thesteps of:directing a second quantity of particulate material into areceiving chamber from said curved conduit of said second segregatingmeans; and selectively providing a delivery stream of gas tointermittently move said second quantity of particulate material into adelivery conduit from said receiving chamber.
 25. A method as recited inclaim 24, further comprising the step of sequencing said intermittentmovement of said second quantity of particulate material from saidreceiving chamber to provide a desired registration between said secondquantity of particulate material and a second selected deposition regionalong a machine direction of said web.
 26. A method as recited in claim1, further comprising the step of sequencing a phased operation of saidtransferring step (c) to provide a desired registration between saidselected quantity of particulate material and a selected depositionregion along a machine direction of said web.
 27. A method as recited inclaim 26, wherein said sequencing step comprises the steps ofoperablyconnecting a line shaft encoder to a primary line shaft; generating areference pulse per each individual product section intended to bederived from said web with a reference signal generator operablyconnected to said line shaft; and receiving and processing outputs fromsaid reference generator and line shaft encoder to selectively sequencethe operation of said selective transferring step (c).
 28. A method asrecited in claim 1 further comprising the step of separating saidparticulate material from a moving mixture of gas and particulatematerial, said separating step comprising the steps of:moving saidmixture of gas and particulate material through a curved conduit havingan inlet section and an outlet section; connecting a particle reservoirin communication with said outlet section; exhausting gas from saidmixture of gas and particulate material through a conduit connected tosaid outlet section of said curved conduit; and providing a gas pressurein said particle reservoir which is relatively higher than a gaspressure in said curved conduit.
 29. A method as recited in claim 1,further comprising the step of detecting said intermittent flow ofparticulate material from said delivery conduit into said formingchamber to ascertain a presence or absence of individual quantities ofsaid particulate material.